The present invention relates generally to differential gear casings for motor vehicles, and particularly to methods of manufacture of differential gear casings.
Differentials are provided in driven axles of vehicles to permit left and right driven wheels to rotate at different speeds while transmitting torque. As is well known, such an arrangement is required to permit a vehicle to turn from a straight line.
Many different kinds of differentials have been proposed, but the most common consists of a casing in which two or four freely rotatable pinion gears are arranged in mesh with opposite side gears of vehicle drive shafts. The casing carries an annular crown wheel which is intended to be driven by a pinion of an input shaft rotatably driven by a vehicle engine.
Casings for differential gears have a number of exacting requirements. They must, of course, have sufficient strength to adequately resist distortion underload. In particular, the casing must be stiff enough to ensure that teeth of internal gears remain in accurate mesh to avoid unnecessary wear and noise. Furthermore, the casing must be capable of being accurately machined to ensure that initial placement of components is accurate and that, for example, bearing surfaces are correctly aligned. This latter requirement can be problematic in casings assembled from two major components.
Yet another difficulty is that the casing design must permit ready assembly thereof. For this purpose, the casing may include windows to permit insertion of pinions, thrust washers and other components. However, such windows inevitably weaken a casing wall, which must be correspondingly stiffened.
There is a need for an improved casing for a differential and an improved method of assembly of the differential.